1. Field Of The Invention
The invention relates to a process for the production of (2R,3E)-4-halo-3-buten-2-ols from the corresponding racemic (2RS,3E)-4-halo-3-buten-2-ols.
2. Background Art
Optically-active secondary .gamma.-haloallyl alcohols, especially the .gamma.-iodoallyl alcohols, are valuable synthesis building blocks for the production of prostaglandins [see, e.g., F. -T. Luo and E. -I. Negishi, J. Org. Chem., 50, (1985), 4762-4766] or of optically active propargyl alcohols, that on their part represent structural elements for various natural substances [see, e.g., T. Ito et al., Tetrahedron Lett., 30. (1989), 7083-7086].
Since racemic .gamma.-haloallyl alcohols are easily obtainable from carboxylic acid chlorides and acetylene via the corresponding chlorovinyl ketones [see, e.g., Y. Kitano et al., Tetrahedron Lett., 28, (1987), 6351-6354], the optically active compounds are suitably produced by resolution of racemates. A known process in this connection is the kinetic resolution of racemates by epoxydation according to Sharpless in the presence of a chiral auxiliary substance (Y. Kitano et al., loc. cit.). Drawbacks of this process are the use of peroxy compounds that in large amounts represent a safety risk, as well as the fact that an enantiomer is lost by decomposing the epoxide formed from it in the subsequent working up.